Taken from https://www.lufthansa.com/us/en/Help-and-Contact
"Can I use my Bluetooth headphones during the flight?You can use your Bluetooth headphones during the entire flight without restriction – even during take-off and landing, unless the crew instruct otherwise."

I believe this may also be country specific, since certain regulations of the country's airspace may be relevant. So, for example if CASA's regulation is no Bluetooth in Australia airspace, then all airlines need to follow that...